Department of Physics, The University of York, Heslington, York YO10 5DD, United Kingdom.
J Struct Biol. 2013 Aug;183(2):270-7. doi: 10.1016/j.jsb.2013.05.017. Epub 2013 Jun 4.
For the understanding of mineral formation processes from solution it is important to obtain a deeper insight into the dynamics of crystal growth. In this study we applied for this purpose a novel atmospheric scanning electron microscope that allows the investigation of CaCO3 particle formation in solution under atmospheric conditions with a resolution of approximately 10nm. Furthermore it permits the in situ observation of the dynamics of crystal evolution. With this tool the precipitation of CaCO3 was studied in the absence and presence of additives, namely poly(acrylic acid) and poly(styrene sulfonate-co-maleic acid) which are known to influence the crystal growth rate and morphology. We determined particle growth rates and investigated the formation and dissolution dynamics of an observed transient phase, believed to be amorphous calcium carbonate. This technique also enabled us to study the depletion zones, areas of lower intensity due to reduced ion concentrations. Ion flux rates were obtained from the depletion zone width, which amounted to several μm assuming the formation and dissolution dynamics of amorphous calcium carbonate being the rate determining process. This assumption was confirmed since the obtained fluxes were found to be in good agreement with fluxes derived from the experimentally observed crystal growth rates.
为了深入了解从溶液中形成矿物的过程，了解晶体生长的动力学机制非常重要。在这项研究中，我们应用了一种新型的大气扫描电子显微镜，该显微镜可以在大气条件下以大约 10nm 的分辨率研究溶液中 CaCO3 颗粒的形成，并且还可以进行原位观察晶体演化的动态过程。利用该工具，我们在没有和存在添加剂的情况下研究了 CaCO3 的沉淀，即已知会影响晶体生长速率和形态的聚（丙烯酸）和聚（苯乙烯磺酸钠-co-马来酸）。我们确定了颗粒生长速率，并研究了观察到的瞬态相的形成和溶解动力学，该瞬态相被认为是无定形碳酸钙。该技术还使我们能够研究耗竭区，即由于离子浓度降低而导致强度降低的区域。离子通量速率是从耗尽区的宽度获得的，假设无定形碳酸钙的形成和溶解动力学是决定速率的过程，则假定耗尽区的宽度达到了几微米。由于获得的通量与从实验观察到的晶体生长速率得出的通量非常吻合，因此证实了这一假设。
